00.17
On a continent where every drop of rain is precious - a quirk of
geological fate has played a seemingly cruel trick on this land.

00.28
The lava and volcanic ash, which form Kenyas' Chyulu Hills, are so
porous that no rivers run here.

00.41
Despite a regular deluge, every last drop soaks away - and
disappears into a labyrinth of lava.

01.01
But what the gods take away with one hand they can give back with the
other, and fifty kilometres away, after filtering through the lava for more
than twenty five years, the water erupts towards the surface - as a
spring.

01.35
This is Mzima spring in Kenyas" Tsavo-West National Park.

Title : MZIMA - HAUNT OF THE RIVER HORSE

01.50
The springs’ pure mineral water would be almost lifeless, but for one
animal.....

02.00
...the hippopotamus, or 'river-horse’.

02.06
It short-circuits the springs’ normal, slow accumulation of nutrients ..... for
the hippos’ dung lays the foundations for a pyramid of life.

02.25
Many creatures make their living on the backs of the hippos.

02.31
Some, like the fish, rely on them directly for food.

02.43
Others, like the predators, rely on the fish. All owe their existence to the
hippos and together make the spring ‘mzima’ - the kiswahili for ‘alive.’

03.01
How the hippos came to live in water is open to conjecture.

03.07
Science suggests that they evolved, not from horses, but from forest-
dwelling, pig-like ancestors which took to the water to keep cool as the
forests contracted.

03.22
Local legend has it that the hippopotamus and his kind had always
wanted to live in the water but this had been denied them by the great
god, Ngai, who feared they would eat his little fish.

03.38
Hot and unhappy, they languished on the banks, becoming increasingly
sunburned, until finally Ngai took pity on them and allowed them into the
water on three conditions:

03.55
He decreed that they should leave the water to feed and eat only grass.

04.00
That they should scatter the dung with their tails so he could check it for
fish bones.

04.07
...and that, every now and again, they should open their mouths as wide
as could be, so he could make sure there were no little fish trapped
inside.

04.17
This the hippos readily agreed to and, to this day, share the water
peacefully with his fish.

04.26
Since then, the hippo has evolved to become truly amphibious, able to
hold its breath for five minutes at a time. Nostrils, eyes and ears have
migrated to the top of the head so it can breathe, and use its main
senses up above with minimum effort. Muscular valves now seal the
nostrils just like the blow-hole of a whale.

04.55
Only a few bristles on its’ nose and the tip of its’ tail, testify to the fact that
the hippo was once hairy.

05.06
Being so amphibious, it is not surprising that hippos mate in the water -
where at least some of the males’ two ton bulk is supported.

05.22
Even suckling takes place submerged.

05.28
For such a voluptuous mammal, the hippo has surprisingly small
mammaries. The baby forms a seal between its tongue and palate so,
even with its mouth partly open, it can suckle without swallowing water.

05.56
But just as the water has had a profound influence on them - so the
hippos have had a huge impact on the spring.

06.08
For the purpose of the spring, the grass-eating hippo is no more than
two tons of mobile compost heap.

06.27
Filled up on land at night, hippos ferment in the shallows by day - each,
an insulated pressure vessel producing twenty kilos of fertiliser a day -
to be dribbled and dropped all over the spring.

06.57
Within a day, the dung will break up to carpet the spring floor. It has the
consistency of chopped wet hay and much of its goodness remains.

07.09
It is food for many in Mzima and is central to its’ web of life.

07.19
The snails are a favourite of barbels, which in turn support cormorants
and crocodiles.

07.30
The fish will also feed directly on dung - especially if it is fresh.

07.40
And just like fresh bread, fresh dung is better if it is warm.

07.54
Such is the demand for it, that whenever it appears it causes a
stampede. The fish have sharp, pointed snouts and are so persistent -
that what started out as a warm breakfast for the barbels, risks
becoming an enema for the hippo.

08.25
When not bothering hippos, a barbel often hangs out with a shovel-
nosed goby - waiting to steal a morsel uncovered by its’ digging.

08.39
The dung is food for all these fish, and for the shovel-nose it can also
be shelter....

08.50
..... and act as a smokescreen to hide it from a predator.

09.06
The dung is probably a baby hippos’ first solid food.

09.22
Like a lot of processed baby-food, the dung might not provide the
goodness of its fresh ingredients, but it does give a youngster
something to chew on.

09.34
The infant doesn’t like to venture out of its depth. Unlike its’ mother, it
can’t hold its breath for much more than half a minute.

10.03
A water scorpion visits the dung pasture for a different reason. After
taking a breath, it cleans up its breathing tube, and then settles down to
camouflage itself.

10.23
This insect is here to hunt fish. Its’ prey are tiny Garra which forage in
the dung.

10.44
Upon capture, it injects its’ victim with enzymes.

10.51
They turn the fishs’ flesh to soup, which the water-scorpion can then
suck up.

11.09
A few hours later, all that remains is an empty husk.

11.21
Mzima is a system fuelled by some 500 tons of hippo dung each year -
but the output from a single hippo would soon dirty the pools, if they
weren’t being flushed through.

11.34
Four springs feed Mzima - with a combined flow of about two swimming
pool-fulls a minute.

11.50
They empty into a series of long pools.

12.00
But then, after only two kilometres, and half a day in the sunshine, the
passage of the water is blocked by a lava flow and it disappears back
underground.

12.16
Just as if a plug had been pulled.

12.24
As in any bath, the water in Mzima is cleanest where it comes in. Near
the source it is so pure, that there is no food here for fish. The barbels
are gathering for a different reason - they are coming up to spawn.

12.57
Their splashing attracts attention.
In the pool the fish could see a crocodile and avoid it - in the rapids
they are vulnerable.

13.14
The croc makes for the channel that the fish used to go up - for what
went up, must come down.....

13.31
The method of fishing is simple and effective - the croc opens its jaws
like a gin trap, closes the back of its throat with a flap valve, and then
waits.

13.54
If a fish so much as touches a tooth it will trigger the trap.

14.23
A croc has good lateral vision, and split second timing. If it looks like a
fish might get past, it can react in an instant.

14.46
Such energy-efficient hunting and explosive reactions, help make the
crocodile the top predator in this pyramid of life.

Part 2

15.10
At Mzima, the pools are kept clean by the flow of pure water, and the
rocks are kept clean by a fish.
Due to its shape and underhung mouth, this fish is known as a fresh-
water shark. It is not related to true sharks though, and such is the
impact of its grazing, that it could better be described as a ‘watery
wildebeest’.

15.40
The move from cleaning a rock to cleaning a hippo - can be made in
the flick of a fin.

16.00
The combined area of skin from Mzimas seventy hippos equals that of a
tennis court - for the sharks it is a giant smorgasbord of dead skin,
algae and parasites.

16.15
To be thoroughly cleaned, a hippo adopts a ‘Trojan Horse’ posture
which stretches open the creases in its skin.

16.31
The sharks’ broad scraping mouths can’t clean inside wounds.

16.38
This surgical niche is filled by the tiny Garra.

16.44
Each type of fish has its own different role.

16.50
The hippos’ lavatory-brush of a tail gets attention from a cichlid.

17.05
While a shark can give a pedicure, the cracks in a hippos’ foot can only
be reached by the pointed snout of a barbel.

17.25
All this pampering gets the hippo so relaxed that it finally offers the fish
what they’ve been waiting for.

17.36
In the whole of Mzima, there is nothing to compare with the rich
pickings in this ivory temple.

18.01
Mouth-cleaning is a service that the hippo actively solicits. Remarkably,
it seems that there are cleaning stations where the fish congregate
and which the hippos regularly visit.

18.21
Even the tongue flops out for attention.

18.30
It is an extraordinary display of co-operation and trust - and only ever
seen when hippos completely relax.

18.57
Often, after mouth-cleaning, a hippo stretches its’ jaws - as if to show
the great god Ngai that there really are no little fish left inside.

19.13
With so many fish hanging around the hippo school, it becomes a focus
for many who would eat them.

19.33
A long-tailed cormorant uses its keen vision for hunting. It can see well
in the clear water and targets the young barbels that feed on hippo
dung.

20.00
The fish might be going down the cormorant, but it is also moving up the
food chain - in this oasis that is supported by hippos.

20.22
The hippos influence on the pools extends to the fruiting trees that
shade the banks.

20.33
In the same way that many of our food plants are now cultivated without
soil, Mzimas’ fig trees and water-pears grow streamer-like roots - to
absorb the water with its hippo-dung fertiliser.

20.49
In return they make a small contribution in the fruiting season.

20.58
The water pears’ berries are relished by vervet monkeys.

21.07
In turn, they pass them on to the barbels and garra, which shoal
beneath the trees when the monkeys are feeding.

21.36
Drawn by the splashing, even a terrapin will try and bob for berries.

21.47
Mzimas’ residents will gorge for a few days while the water pears are in
fruit, but it is not a free lunch - in return, they will scatter the trees’ seeds
throughout the pools.

22.06
After a dessert of water pear and a dip in the pool, where better to
warm up and digest than on an island in the sun?

22.44
A wagtail visits the hippos to hunt for biting flies as she has chicks to
feed.

22.58
She is a spoke in the wheel of life that radiates out from the hippos.

23.07
On her way to the nest she stops to dip her catch - not to wash it, but to
wet it. The nest is exposed to the full force of the sun but, by using her
catch as a sponge, she gives her chicks a cool drink, each time she
brings food.

23.36
Almost eight months after she mated, a pregnant female hippo leaves
the school and lies up in the shallows.

23.47
She will wait out her time alone - and give birth secretly in the reeds.

23.59
Any unusual behaviour attracts attention.

24.06
A crocodile is no match for an adult hippo, but it is a real threat to an
infant. It can go months without feeding so it will hang around - waiting
for the baby to be born.

24.33
In Mzima, size for size, the most voracious predators are water beetles.
They are also prime scavengers and fight over the carcase of a frog just
as a pride of lions would a wildebeest.

24.51
They become so engrossed in feeding that they fail to recognise the
danger ahead - for just as Mzima springs from the ground, so it returns
to it....

25.16
Above water, beetles are equally important scavengers.

25.26
Carrion beetles are often the first to find a carcase.

25.38
Attracted by the smell, they bury through to consume what they can.
Their tenure will be brief - nothing this big dies close to the spring
without attracting the attention of a crocodile.

26.07
It is difficult for a single croc to open a carcase - even for a giant male. A
crocodile has no cutting teeth, so it must bite on and spin, to try and
break pieces off.

26.46
Set adrift in their thousands, the carrion beetles will spread the bounty
of the carcase throughout the spring.

26.57
The beetles are so popular, that for an hour or so, Mzima is gripped by
a natural beetlemania.

27.19
Many of the smaller creatures can’t feed directly on the carcase, but they can consume it packaged in a beetle.

28.06
Now that the dominant male has opened the carcase - smell, and the
sound of splashing will draw others in.

28.25
Initially they are wary of the large male but they slowly edge closer,
testing the water.

28.46
If their approach doesn’t provoke an attack then they will lose their
inhibitions and feeding will turn into a frenzy.

29.56
The female has given birth - at 40 kilos, her baby is no larger than a
chubby labrador.

30.13
The first few weeks are the most vulnerable time in a hippos life - for the
tiny baby is eager to explore, and doesn’t yet know what a crocodile is.

30.30
The mother is the calfs’ only protection.

30.44
From now on, she must be constantly on guard - if her baby is to have
any chance of surviving.

Part 3

31.27
The build-up of nutrients in most waterholes is a sporadic and seasonal
process.

31.42
The effects of animals breaking up the topsoil and wind-blown dust,
combine to gradually fertilise the water.

31.52
In Mzima, the hippos bypass that slow accumulation - for what they
produce in a day would take wind and weather a season to achieve.

32.23
The hippos’ input is not confined to their dung for when it rains, their
paths to night-time feeding grounds channel the muddy runoff down into
the spring.

32.51
So in one way or another, thanks to the hippos, the pools get a
transfusion of nutrients and become a richer place for all who live in
them

33.11
The baby hippo now stays very close to its’ mother.

33.18
She will not risk introducing it to the school for a couple of weeks, until
it has firmly bonded to her. In the meantime, they explore the pool
together and she shows it places where it can reach the surface to
breathe.

33.38
As in most societies, a new-born excites attention, and the schools’
dominant male comes to investigate.

33.57
A male can be a threat to a youngster that even its’ mother cannot deal
with for, on rare occasions, males have been known to kill infants.

34.17
The baby must not get separated now.

34.29
By presenting her rump and flapping her tail, the female is being very
submissive.

34.37
He is the father of her calf, but still, it would not do to provoke him.

34.52
Away from the log, the baby finds it difficult. It tires rapidly as it must leap
to the surface to breathe ... but it has learnt the most important lesson -
to always stick close to mum.

35.12
Back on its perch, it falls asleep quickly - as only a baby can.

35.37
Vervet monkeys give birth at the same time of year.

35.44
A python is a principal predator.

35.48
From the start, the females keep their babies in the troop where there
are more eyes to look out for them.

36.24
They react to the python not by fleeing, but with alarm calls.

36.34
Alerted by the calls, the troop will follow the snake - for as long as they
can keep it in view, then it is not a threat.

36.52
Milky eyes mean that the python can barely see, as its’ old skin is
starting to separate. It is not hunting but will shortly moult and is going
to the spring to soak.

37.15
In trying to keep it in sight, a youngster makes the mistake of going a
branch too far....

37.46
Soaking for a day or two, will help soften the pythons’ old skin and
make shedding easier.

37.58
For fresh-water prawns, the peeling skin represents a huge boost of
protein.

38.13
Like the springs’ fish, they have adapted their feeding behaviour to take
advantage of an unlikely source of food.

38.23
The python is not quite ready to shed all its’ skin, but it puts up with the
attention until one ambitious prawn decides to try and have its’ snake
and eat it.

38.50
To a prawn, this is manna from heaven.

38.58
The python will move on to where it can soak in peace.

Part 4

39.21
In Mzima, the female is now ready to introduce her calf to the school.

39.28
Already, the baby is scarred on its rump - not by a crocodile, but by a
hippos’ canine teeth.

39.42
The next two minutes are what mother and calf have spent two weeks
preparing for. It is critical now that the baby doesn’t leave her side.

40.00
When a young male comes to investigate, he challenges the female.

41.57
A hippo infanticide is incredibly rare - it has been witnessed only a
handful of times in the past fifty years. On each occasion the killer was
an adult male who had recently taken over a school. This time it was a
young male, who killed a male calf - it may be that in a society where
only the dominate male gets to mate, a young male can improve his
chances, of getting to the top, by killing a potential rival at a very early
age.

42.33
It is some time before the mother can reclaim her baby.

43.00
When she does, it is too late. In vain, she tries to nudge it awake as if it
were sleeping.

43.16
Then she tries to lift it to the surface to help it to breathe.

43.57
In time, the dead baby will become part of the spring.

44.11
Just as a hippo contributes to Mzimas’ richness in life - so it will in
death.

44.22
An infanticide is a terrible event, but it is rare and remains an enigma -
most babies join the school and stay safe and supported.

44.46
So much about them is unknown - but what we do know is that they are
the life-support system for the spring, and no life support system should
be taken for granted.
Outside the protection of a National Park, a nearby spring has lost its
hippos and as a result, is almost lifeless. Once the haunt of the river
horse - this spring is now haunted by them

45.15
Today, we wouldn’t even know they once lived here - if it wasn’t for a
secret, deep underground. Over hundreds of years, hippos have
entered this narrow passage and become lost in a flooded cave.

45.38
Unable to find the single small exit, they panicked and drowned.

45.46
Each time one died, it attracted crocodiles which suffered the same fate.

45.56
Today their skeletons lie entwined in a trench - ancient adversaries in
an eternal embrace.

46.18
The sand is made up of almost pure bone - for, the skeletons have
been worn down, over centuries, by a perpetual sandstorm.

46.31
This quicksand is the source of the spring, where water is forced up
from deep underground - all fuelled by rain which fell on lava decades
ago.

46.49
Without its hippos, the entire system now supports only a few small fish.

47.07
In Mzima, a hippo skeleton lasts just a few years, for the rasping action
of a thousand tiny mouths ensures that it will soon be recycled as fish
bone.

47.28
When the great god Ngai allowed the hippos to live in the water all
those years ago, he could never have imagined the bond they would
form with his fish. Today, hippos and fish rely on each other and share
an extraordinary relationship.

47.47
In turn, they support all the other animals living in the spring.

47.56
They are the foundations of a pyramid of life, in this spring that is
‘Mzima’.